Arrangement in an adjustable chair

ABSTRACT

A device for an adjustable chair, where the back of the chair, at a first mounting site on each side thereof, is pivotally connected to respective side members of the chair, and at a second mounting site forms a hinged connection with a rear part of the chair set frame, where the chair seat frame, at a front mounting site on each side thereof, is slidably connected to a respective side member along a front guide which forms a part of the side member. The first mounting site on the chair back is designed to slide along a rear, forward and downward inclining guide in the side member, and the seat frame has on each side a rear mounting site between said front mounting site and said second mounting site for the chair back, said rear mounting site forming a slidable connection with a guide in each respective side member, which is located between the front and rear guides when seen in the longitudinal direction of the side member which is either horizontal or inclines slightly forward and upward.

BACKGROUND OF THE INVENTION

The present invention relates to a device for an adjustable chair, wherethe back of the adjustable chair at a first mounting site on each sidethereof is pivotally connected to respective side members of the chair,and at a second mounting site forms a hinged connection with a rear partof the chair seat frame, where the chair seat frame, at a front mountingsite on each side thereof, slidably connected to one of the torespective side members along a front guide which forms a part of theside member, wherein said first mounting site on the chair back isdesigned to slide along forward and downward inclining rear guide in theside member, and wherein the seat frame on each side has a rear mountingsite between said front mounting site and said second mounting site forthe chair back, said rear mounting site forming a slidable connectionwith a central guide in each respective side member, which is locatedbetween the front guide and the rear guide when seen in the longitudinaldirection of the side member.

From the prior art, reference shall be made to GB Patent No. 1278501, DEPatent No. 3822877, U.S. Pat. No. 4,759,561, and also a chair marketedunder the trade mark STRESSLESS®. The last-mentioned chair type is alsocharacterised, inter alia. in that the centre of gravity of the body inrelation to the chair is kept virtually constant, usually near or abovethe central frame of the chair, if the chair is of the swivel type. Amajor aspect of the known chair type is, however, that when the backtips backward the lower end of the chair back remains at the same levelas the back edge of the chair seat. This is due to the seat back and thechair seat being connected to one another at the lower edge of the chairback and the rear edge of the chair seat, respectively. When the chairuser leans backwards in the chair, he may experience the sensation ofthe chair back apparently "climbing" up his back a little. On leaningback it is, of course, important that the head rest and similar are feltto be approximately in the same place irrespective of the sittingposition.

This problem is nonetheless important in connection with adjustablewheelchairs, where being able to adjust the back in relation to a fixedseat or having the seat and back then rigidly connected to one anotherand be tiltable or adjustable as a unit are typical configurations.Furthermore, it has been known in connection with adjustable wheelchairsthat these require at least one support leg which projects out behindthe large wheelchair wheels to prevent the chair from tipping backwardwhen the chair user leans back in the chair.

SUMMARY OF THE INVENTION

It has thus been one of the objects of the present invention to providea device for an adjustable chair of the aforementioned type, wherein theaforementioned drawbacks both in normal adjustable chairs of this kindand especially in wheelchairs can be remedied. The invention seeks inthe first place to provide good sitting comfort in an adjustable chairof this kind, and in the event of the invention being applied for use ina manual wheelchair, the otherwise good sitting comfort of the comfortwheelchair will be capable of being combined with the driving andtransport properties of the active wheelchair. The object of the presentinvention, especially in connection with a wheelchair, is to be able tocombine an "active driving position" with a "passive resting position"in one and the same wheelchair.

According to the invention, the device mentioned by way of introductionis characterized in that the front guide is inclined forward and upwardand forms an angle with the horizontal in the range of 10°-45°, that thecentral guide forms an angle with the horizontal in the range of 0°-15°,and that the rear guide is slightly curved, and forms an angle with thehorizontal in the range of 15°-45°.

In a preferred embodiment, the central guide is inclined forward andupward with an angle not exceeding 15° relative to the horizontal.

According to a further embodiment of the device, the side members arepreferably made of extruded aluminium, said guides being formed bymilling out grooves in a side surface of the side member. Said groovesmay optionally be provided with a slide lining.

The front mounting site and the front guide are suitably formed suchthat friction therebetween is adjusted by means of a steplesslyadjustable mechanism.

In order to ensure that the chair user does not experience the sensationof the chair back apparently "climbing up" his back, the back of thechair is to advantageously provided at the bottom with a frame memberwhich projects forward in the longitudinal direction of the chair andforms an obtuse angle with the upwardly projecting part of the back, thefree end of the frame member forming a part of said second mountingsite.

As mentioned above, the present device exhibits special advantages inconnection with use in a wheelchair, although the device may just asreadily be used for any form of easy chair.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail below with referenceto the accompanying drawings.

FIG. 1 is schematic illustration of the device according to theinvention applied to a wheelchair structure.

FIG. 2 is a more detailed view of the device according to the inventionas shown in FIG. 1.

FIGS. 3, 4 and 5 show the application of the device according to theinvention for a wheelchair in different positions of use.

FIGS. 6, 7 and 8 show in an enlarged version the different settings ofthe seat and the back in relation to one another as shown in therespective FIGS. 3, 4 and 5 without wheelchair parts and a wheelchairuser being included in the drawing.

FIG. 9 shows a cross-section of a chair seat with side members accordingto the invention.

FIG. 10 shows the section X in FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, the device according to the invention is shown in connectionwith a wheelchair solution. The wheelchair parts are only illustratedschematically in order not to complicate the understanding of the modeof operation of the device.

The back 1 of the chair is connected to a chair back frame 2 which, at afirst mounting site 3 on each side of the chair back, is moveable inrelation to respective side members 4 on the chair, and at a secondmounting site 5 forms a hinged connection with a rear part of the frame7 of the chair seat 6. The frame 7 of the chair seat, at a rear mountingsite 8 on each longitudinal side of the seat, is slideably connected tothe respective side member 4 along a front, forward and upward incliningguide 9 which forms a part of the side member. The first mounting site 3on the frame 2 of the chair back 1 is designed to slide along a rear,forward and downward inclining guide 10 in the side member 4. The seatframe 7, on each side of the seat, has a rear mounting site 11 locatedbetween said front mounting site 8 and said second mounting site 5 forthe chair back 1. The rear mounting site 11 forms a slideable connectionwith a guide 12 in the respective side member 4, which is central whenseen in the longitudinal direction of the side member 4. The centralguide 12 may either be approximately horizontal or inclined slightlyforward and upward when seen in the longitudinal direction of the chair.

The small wheels 13 of the wheelchair may be pivotally connected via awheel fork 14 to a front part of the respective side member 4 of thechair. The large wheels 15 of the wheelchair may in a known way per sebe connected to the chair side member 4. The chair frame 7, at the frontedge thereof, may optionally be provided with a downward projecting part7' for the support of a foot rest 7".

In order to secure a locking of the adjusted position of the chair seat6 and back 1, a stepless, adjustable clamp coupling, schematicallyindicated and having the reference numeral 16 in FIG. 2, may be used ina known way per se. This clamp coupling may consist of an adjustingwheel and a friction disc, where the friction disc (not shown) comes torest against the outside of the side member. The adjusting device may berotatably connected to the said front mounting site on the seat frame.As can be seen from FIG. 1, the chair back may be provided with aheadrest 17, which is of particular importance in connection with usefor a wheelchair.

As can be seen clearly from the skeleton drawings in FIGS. 1 and 2, thechair back frame 2 has at the bottom a frame member 2' which projectsforward in the longitudinal direction of the chair and forms an obtuseangle with the upwardly projecting part of the chair back 1. The freeend of the frame member 2' forms a part of said second mounting site 5as is shown.

In FIGS. 3, 4 and 5, the device according to the invention is shown inconnection with use in a wheelchair structure. The person sitting in thechair is indicated by means of the reference numeral 17 and the centreof gravity of the person is indicated by means of reference numeral 17'.The horizontal distance from the centre of gravity 17' to the centre ofrotation 13' between the small wheel 13 and the supporting fork 14 isdesignated the distance L1. In a similar way, the horizontal distancebetween the centre of gravity 17' and the centre of rotation 15' of thelarge wheels 15 in connection with the side member 4 is designated L2.As can be seen from FIGS. 4 and 5, together with FIG. 3, the horizontaldistance between the centre of gravity 17' and the centres of rotation13' and 15' respectively, will essentially be the same irrespective ofthe position the chair user 17 assumes in the chair. It will alsoclearly be seen that the chair back 1 in the different sitting positionshas not "climbed up" the chair user's back. This is due not least to thefirst mounting site 3 of the chair back moving downward when the chairuser leans backward, whilst the chair seat is moved forward and upward.In the sitting position shown in FIG. 4, the chair user is in a mediumresting position in the chair, whereas in FIG. 5 the full restingposition has been assumed.

The reciprocal movements of the chair back, seat and mounting sites willbe explained in more detail in connection with FIGS. 6, 7 and 8. Thesame reference numerals as have been used in the preceding figures arealso used in FIGS. 6-8, insofar as they are necessary for theexplanation.

As can be seen from FIG. 6, where the chair back 1 is shown in an erectposition, the first mounting site 3, e.g., a pin or a roller, will belocated at the rearmost end of the rear guide 10. In a similar way, therear mounting site 11 on the seat frame 7, e.g., in the form of a pin ora roller, will be located in the rear end of the central guide 12.Similarly, the front mounting site 8 on the seat frame 7, e.g., in theform of a pin or a roller, will be located at the rear end of the frontguide 9. When the chair user leans back, as is shown in FIG. 4, whichcorresponds to the situation which can be seen in FIG. 7, the firstmounting site 3 will move downward along the guide 10. The rear mountingsite 11 of the seat 6 moves forward correspondingly along the guide 12.Similarly, the front mounting site 8 will move forward and slantwiseupward along the guide 9. This movement has been completed in FIG. 8,where the respective mounting sites 3, 11 and 8 have reached theirforward end positions in the respective guides 10, 11 and 9. In thisposition, the seat has an upward and forward inclining position,approximately parallel to the longitudinal direction of the guide 9.Owing to the movement of the first mounting site 3 along the guide 10,the second mounting site between the frame member 2' of the back and theback edge of the seat frame 7 will also necessarily move both downwardand forward. Seen in relation to FIG. 6, the back edge of the seat 6 andthe lower part of the chair back 1 will have moved apart from oneanother, whilst the lower part of the chair back lies below the level ofthe upper back edge of the seat. In this way, the user is prevented fromhaving the sensation of the chair back apparently "climbing up" his backwhen he leans back in the chair. The use of the rear mounting site 11and also the guide 12 is essential to prevent the chair user, on makingfurther attempts to lean back, from causing the chair back to move evenfurther backward in order to assume a horizontal or downward andbackward lying position, as the mounting site 5 in this case wouldascend toward the top edge of the side member. The interaction betweenthe different mounting sites 3, 5, 11 and 8, and also the use of theguides 10, 12 and 9 in connection with the mounting sites 3, 11 and 8,is thus essential in order to achieve the desired function of thedevice. The use of the projecting member 2' of the chair back frame 2also constitutes an essential part of the overall structure.

FIGS. 9 and 10 are purely schematic illustrations of a practicalembodiment which illustrates the respective mounting sites 3, 11 and 8,the associated guides 10, 12 and 9, the seat frame 7 and the sidemembers 4. The side members 4 are made of extruded profile bodies. Theextruded profile shown in the drawings is not necessarily limiting forthe embodiment in question.

By means of the present invention, a structure is thus achieved, wherethe possibilities of good sitting comfort and tilting are achieved inthat the sitting unit is tilted with the centre thereof in the centre ofgravity 17' of the body 17. The centre of gravity of the body inrelation to the chair is thus kept almost constant, seen in thehorizontal direction of the chair, but also in the vertical directionthereof. As can be seen from FIGS. 3-5, the L1/L2 ratio is the same inall adjustable positions of the chair device.

With the chair according to the invention, the advantage is achievedthat both the seat angle and the back angle are changed simultaneously,but with a greater angular excursion for the back. This results in abetter sitting position for the chair user. The present structure alsoenables a chair user, e.g., a disabled person, to adjust the tilting ofthe chair himself without any help from an escort.

By virtue of the fact that the centre of gravity of the body in relationto the longitudinal direction of the chair is kept virtually constantduring the adjustment of the chair, a minimum reduction of thereciprocal centre distance between the wheels 13 and 15 is achieved,which helps to improve the driving properties without this being to thedetriment of the backward tilting safety of the wheelchair.

When constructing the supporting structure, a principle is used inconnection with wheelchairs where the sitting unit (corresponding to theback frame 2, including back frame member 2', the seat frame 7 and legsupports 7', 7") as a separate unit constantly follows the user'smovements from an active to a passive position, and vice versa.

The sitting unit moves between the two side members 4'. The position ofthe guides 10, 12 and 9 gives the angular path along which the sittingunit will move. The side members 4 will in reality correspond to thecomplex and heavy carriage frame in a conventional wheelchair structure.In addition, these side member profiles, in a simple manner, will serveas attachments for wheels, wheel brakes, arm rests 18, handles and soforth.

The present structure makes possible the use of a relatively low numberof parts. The use of side members in the form of extruded aluminiumprofiles will give greater flexibility with a view to model variationsand different chair sizes, at the same time as a simple structure isachieved. The chair will be simple to mount and adjust and will providepossibilities for rational transport and storage. The side members canbe connected by means of stabilising bars 19. Optionally, the sidemembers at the front edge and back edge thereof can be provided withstabilising cross braces 20, 21 as indicated in FIG. 2.

As can be seen from the drawings, the rear guide is preferably slightlyU-shaped. It may form an angle with the horizontal in the range of15°-45°, in a preferred embodiment of the invention. Furthermore, thecentral guide 12 may form an angle with the horizontal in the range of0°-15°. The front guide 9 should preferably form an angle with thehorizontal in the range of 10°-45°. As also can be seen from FIG. 10,the grooves which are made in the side members 4 to create therespective guides 10, 12 and 9 may have a slide lining, so that there isno risk of unwanted wear occurring in said grooves on the side membersof the chair.

What is claimed is:
 1. A device for an adjustable chair, where the backof said adjustable chair, at a first mounting site on each side thereof,is pivotally connected to respective side members of the chair, and at asecond mounting site forms a hinged connection with a rear part of achair seat frame, where the chair seat frame, at a front mounting siteon each side thereof, is slidably connected to one of the respectiveside members along a front guide which forms a part of the side member,wherein said first mounting site on the chair back is designed to slidealong a rear, forward and downward inclined guide in the side member,and wherein the seat frame on each side has a rear mounting site betweensaid front mounting site and said second mounting site for the chairback, said rear mounting site forming a slidable connection with acentral guide in each respective side member, which is located betweenthe front guide and the rear guide when seen in the longitudinaldirection of the side member, characterized in that the front guide isinclined forward and upward and forms an angle with the horizontal inthe range of 10°-45°, that the central guide forms an angle with thehorizontal in the range of 0°-15°, and that the rear, forward anddownwardly inclined guide is slightly curved, and forms an angle withthe horizontal in the range of 15°-45°.
 2. The device of claim 1,wherein the side members are made of extruded aluminum.
 3. The device ofclaim 1, wherein the front mounting site and the front guide are formedsuch that friction therebetween is adjusted by means of a steplesslyadjustable mechanism.
 4. The device of claim 1, wherein a bottom of theback of the chair has a frame member which projects forward in thelongitudinal direction of the chair and forms an obtuse angle with anupward projecting part of the back, a free end of said frame memberforming a part of said second mounting site.
 5. The device of claim 1,wherein the central guide is inclined forward and upward with an anglenot exceeding 15° relative to the horizontal.
 6. The device of claim 1,wherein the guides include grooves milled out in a side surface of theside member.
 7. The device of claim 6, wherein grooves are provided witha slide lining.